Conventionally, as disclosed in Japanese Patent Laid-Open No. 2009-3685 (JP '685), a data recording apparatus for recording data that represents a system operation condition of a system when an event occurrence of the system triggers the recording of the data. The data recording apparatus is equipped with an analysis object data temporary save unit for storing analysis object data for a recent period of a predetermined time length or for a predetermined number of data acquisition times; an event occurrence determination unit for determining an occurrence of an event based on event occurrence determination data; and a data storage unit for storing the data stored in the analysis object data temporary save unit in association with an event data after a predetermined time period from the determination of the occurrence of the event.
As described above, due to the storage of the event data in association with the analysis object data, the device in JP '685 enables event analysis of a complicated event by using various event factors such as an event type, an event source, an event condition, and the like. Further, because event data itself is associated with the analysis object data for the distinction of event factors, the stored amount of data is decreased to use only a small area of a memory.
The data recording apparatus in JP '685 is configured to have only one electronic control unit (ECU) to provide an analysis object data temporary save unit, an event occurrence determination unit, and as well as a data storage unit, for storing, in the memory, the analysis object data generated during a predetermined period before and after the occurrence of an event. Therefore, when the detection of the occurrence of the event and the storage of the analysis object data are performed by only one electronic control unit, the required data is successfully stored.
However, for example, an in-vehicle control system controlling a travel condition of a hybrid vehicle has various devices under its control, such as an engine, a motor, brakes, a transmission, a steering, a battery, and the like. Therefore, multiple electronic control units are installed in a vehicle for controlling the devices, and each of the devices may be controlled under cooperative operation of the multiple electronic control units.
When multiple electronic control units are installed in such manner, the data which should be recorded at the time of the occurrence of an event may exist in a dispersed manner in those electronic control units. Therefore, even when the occurrence of an event is detected in one of the electronic control units, the recordation of all of the required data at the time of such occurrence of an event may be difficult.